Borrowed fron another source...Easier than typing...
 
Setting a default route is easy:
 
route add default xxx.xxx.xxx.xxx  
 
is all it takes.  However, unlike NT systems (which stick it in the Registry), that won't survive a reboot.
 
If you have 5.0.6, you have the file /etc/default/tcp and you can edit that to add the route to the
 
GATEWAY=
 
line.
 
If you have 5.0.4 or 5.05, a nice place to add routes is /usr/internet/etc/sco_ip/routes.  The startup script /etc/rc2.d/S90iproute reads that file and sets routes.  The format is pretty obvious:
 
# comments are ok
# simple form
net default 10.1.1.3
# it's smart enough to delete the previous default
net default 192.168.1.2  
# routes to specific hosts
host 192.168.1.8 10.1.1.7
# netmasks optional
net 192.168.1.0 10.1.1.3 255.255.255.0
# if field 1 isn't host or net, it's ignored
happiness 172.16.80.10 10.1.1.1
sanjose 172.16.80.10 10.1.1.1
 
Prior to 5.0.4, some folks would  edit /etc/tcp to add the "route add" line.  That has the advantage  of letting you use tcp stop and tcp start and have the route set, but keep in mind that an upgrade will overwrite /etc/tcp.
 
The typical solution pre 5.0.4 is to add a /etc/rc2.d/S99route file and add the "route add" command to it.(the file does not exist- you have to create it).  Remember to make it executable (chmod 755).
 
Keeping the route on any version can be affected by running  programs like routed- a router on the network may have a different idea what routes should be set, and it may send RIP updates- if routed is running on your system, your routing table will change.  Comment routed out of /etc/tcp to disable it.
 
Note that a device on the other side of a router has to have a route BACK to you also.
 
Also, you need to reboot or manually type the route add command to have this work immediately